Rectilinear fluid shock absorber



March 18, 1952 B. E. o'coNNoR ETAL 2,589,282

RECTILINEAR FLUID SHOCK ABSORBER Filed Aug. 25, 1948 2 SHEETS--SHEET l March 18, 1952 B. E. o'coNNoR ET A1. 2,589,282 RECTILINEAR FLUID SHOCK BSORBER Filed Aug. 25, 1948 2 SHEETS- SHEET 2 Patented Mar. 18, 1952 RECTILINEAR FLUID VSHCK ABSORBER Bernard E. OCcnncr, Buialo, and Richard E.

Henrich, Kenmore, N. Y., assignors to HoudaillesHershey Corporation, Detroit, Mich., a

corporation of Michigan Application August 25, 1948, Serial No. 46,064

(Cl. 18S-97) 9 Claims. 1

This invention relates to a hydraulic check unit, and particularly to an improved hydraulic check unit adaptable for checking the movements of the picker stick of the loom. In the copending application of George H. Huierd, Serial No. 37,950 filed July 9, 1948, and assigned to the assignee of this application, there is disclosed and claimed a hydraulic check unit which is particularly adaptable for checking the movements of the picker stick of a'loom. This application constitutes further improvements in the construction of such a hydraulic check unit, and in particular, provides an improved expansible volume reservoir chamber for accommodating quantities of fluid temporarily displaced from the primary cylinder chamber as occurs when the hydraulic medium undergoes thermal expansion or when the hydraulic medium is displaced by the entry of the piston rod into the primary cylinder chamber or as the result of the relative displacement occurring when the piston undergoes rapid movement.

As is well known, the picker stick of a fly shuttle loom, and hence the linkage which controls the movements of such picker stick, are subject to very rapid acceleration in both directions of its movement. When a hydraulic check unit is applied to a picker stick control linkage in the manner described in the above identied pending application of George H. Hufferd, it has been found that the movements of the piston of the check unit throughout those portions of the stroke of a, picker stick wherein checking is not desired, such as in the initiation of the power stroke, is so rapid as to temporarily displace an excess of fluid from the cylinder chamber, in which the piston operates, through the throttling apertures into the reservoir chamber. The volume of the cylinder chamber available for containing the hydraulic medium also varies as the piston rod enters and leaves the chamber. After a fly shuttle loom has been in operation over a short period of time, the hydraulic check unit will be subjectedto a normal operating temperature of approximately 150 F.` Thus, the yhydraulic medium will undergo a noticeable increase in volume. It is therefore necessary that the reservoir chamber incorporate some means for permitting the ready accommodation of displaced fluid, yet at the same time prevent the addition of any airvto the cylinder chamber of the check unit which would result in the check device becoming unreliable in operation.

Accordingly, itis an object of this invention to provide lan improved hydraulic check unit in- 2 corporating an expansible volume reservoir chamber of unusual simplicity and reliability.

Another object of this invention is to provide an improved unitary casing for hydraulic check units which not only denes a primary chamber within which the piston of the check unit opcrates, but in addition denes a vertically superimposed reservoir chamber in uid communication with throttling apertures in the primary chamber to receive fluid displaced from the primary chamber and accommodates such fluid-by compression of entrapped air at the top portions of fthe reservoir chamber.

Still another object of this invention is to provide an improved construction of a iilling opening for a reservoir chamber of the typehaving a trapped air space in the top portion thereof, wherein a depending sleeve defines the lling opening `and provides a convenient indication of the properfluidlevel within the reservoir chamber which will provide the required height of trapped air space.

The specific nature of the invention, as well as other objects and advantages thereof, will become apparent to those skilled in they art from the following detailed description of theannexed sheets of drawings, which, 4by way ofpreferred example only, illustrate one specic embodiment of the invention. f

On-the drawings:y Y

Figure 1 is a side elevational View of a picker sticklinkage -for-a loom incorporating a hydraulic check unit embodying this invention.

Figure 2 is a longitudinal sectional view taken through the hydraulic check unit incorporated in the assemblage of Fig. 1.

Figure 3 is a sectional view taken on the plane III-III of Fig. 2.

Figure 4 is a reduced scale, top elevational view of the assemblage of Fig. 1.

As shown on the drawings:

While this invention will be particularly described and illustrated in connection with the application of a hydraulic check unit tocheck the `movements vof a picker stick of a loom, it`will so that the top end of the stick traverses a substantially horizontal, straight line path. Such linkage, which is described and claimed in George H. Hufferds copending application, Serial No. 37,951, led July 9, 1948, now Patent No. 2,566,890, issued September 4, 1951, and assigned to the assignee of this application, may comprise a primary bracket I2, rigidly secured to the rock shaft I0, and secondary bracket I3 which is connected to primary bracket I2 by a pair of pivoted links I4 and I5. Links I4 and I5 may each constitute two identical parallel link elements or a single link, depending entirely upon the nature of their pivotal supports. The location of the pivot points of links I4 and I5, as well as the relative dimensions of such links are selected in the manner described in the above referred to copending application, so that the picker stick I I can move only in a path which will result in the upper end of the stick moving along the lay (not shown) of the loom in a substantially horizontal, straight line path.

Thus, primary bracket I2 constitutes an integral casting having a split extension portion I2m defining a cylindrical recess to receive the end of rock shaft I and being clamped to rock shaft I0 by a bolt I2e and a key I`2;f which is drawn into clamping engagement with the rock shaft I0 by a nut I2g.

In addition, primary bracket I2 defines three spaced pivot bearings I2a, I2b and I2c respectively. Pivot bearing I2a is located in slightly depending relationship with respect to the rock shaft I0, and adjacent the end thereof, and provides pivotal support for one end of the link I5. Pivot bearing I2a is preferably of bifurcated construction and thus surrounds the end of link I5. A pin I6 pivotally connects link I5 and pivot bearing I2a, and link I6, if desired, may incorporate an eccentric portion (not shown) in the manner described in detail in the above referred to copending application so as to permit limited adjustment of the elective length of link I varying the angular position of the pivot pin I6.

Pivot bearing I2b on primary bracket I2 1s also of bifurcated construction and is located directly above the end of rock shaft I0 to provide pivotal support for the cylinder element ZI of an hydraulic check unit 20 embodying this invention and to be described in more detail later.

Lastly, pivot bearing I2c is defined by a yokeshaped portion I2d of primary bracket I2, and such pivot bearing is disposed in generally triangularly spaced relationship with respect to pivot bearings I2a and I2b and pivotally journals one end of the links I4.

The secondary bracket I3 is of generally reversed E-shaped configuration, and may be conveniently formed by a riveted assemblage of two half parts, as indicated by rivets I3c. The back side of the upright portion of bracket I3 is suitably apertured as indicated at I3d (Fig. 4) so as to conform to and snugly partially surround the bottom portion of the picker stick II. Picker stick II is rigidly clamped in recess I3d by a plurality of U-shaped clamps I1 which are suitably threadably secured to secondary bracket I3 by bolts Ila.

Secondary bracket I3 likewise defines three pivot bearings which are respectively located yin lthe ends of its arm portions. Thus a bifurcated pivot bearing I3a is formed in the end of the lowermost arm portion and pivotally journals the other end of link I5. A bifurcated pivot bearing I3b is mounted in the end of the top arm portion and pivotally journals the end of the piston rod 26 of the hydraulic check unit 20. Lastly, a pivot bearing I3c is provided in the end of the intermediate arm of secondary bracket I3 and pivotally journals the other ends of links I4. All of the pivot bearings heretofore mentioned, except pivot bearing I2a, embody conventional pivot pins and grease fittings'Q.

Conventional mechanism is provided for producing the required oscillating movement of the picker stick II, such as a lug strap (not shown) which engages an intermediate portion of the picker stick I I. 'The lug strap is operated by conventional mechanism so as to periodically shift the picker stick II from its extreme outward position to its extreme inward position, and in so doing, accelerates the picker stick II so rapidly that the shuttle (not shown) which is in contact with the upper end of the picker stick II, is violently thrown to the other side of the loom. After the shuttle is thrown, the inward movement of the picker stick II is checked by the hydraulic unit 28 in a manner to be described and the picker stick II is brought to rest at its extreme inward position. Thereupon, a torsion spring 4D, operating between secondary bracket I3 and link I5 is effective to urge the picker stick I I outwardly at least to an intermediate neutral position wherein a leaf spring stop portion IIa carried by an arm 4I pivotally secured to secondary bracket I3 by an eccentric pin 43, engages a xed pin 44 transversely mounted in the primary bracket I2. At this point, the picker stick II is properly positioned to receive the initial contact by the shuttle when the shuttle is thrown back from the other side of the loom. The construction of the leaf spring stop 4I and the eccentric adjusting mechanism therefor is described in detail and claimed in George H. Hufferd copending application, Serial No. 37,952, led July 9, 1948, now Patent No. 2,519,372, of August 22, 1950, and assigned to the assignee of this application, and reference should be had thereto for a more detailed description.

Upon the contact of the returning shuttle with the top end of the picker stick I I, the stick II is violently driven outwardly, and such outward movement must be checked by the hydraulic unit 20 to rapidly and smoothly bring the picker stick II to rest without producing a rebounding of the shuttle therefrom or permitting excessive forces to be developed in the picker stick II or any portion of its control linkage. Furthermore, the picker stick I I must be brought to rest in substantially the same position each time so that the shuttle is properly positioned in the shuttle box.

From the foregoing discussion, some of the principal operating characteristics of the hydraulic check unit 29 have been indicated. Such unit must be of the double acting type and preferably provide a checking action only at each end of the opposite directions of movement of the picker stick II. In addition, as is well known, the operating characteristics of the loom vary substantially with temperature and humidity conditions as well as with wear of various component parts thereof. As the result, it is essential that the checking action exerted by the hydraulic check unit 20 be conveniently manually adjustable, at least with respect to the effective checking action exerted upon the outward,vor shuttle catching stroke of the picker stick II, while the loom is operating, so that optimum conditionsof checking, and hence uniformity of operation may be maintained. Furthermore, it is essential that the checking unit produce a minimum lresistence to suc `l lduringfthe" y or shuttle` throwing fs reke,V which constitutes the movement `yof' the'pickjer `stick from itsf extreme outvvardA position toward its extreme 'inward poy sii-zien; l l

The foregoingV characteristics are admirably supplied-by'anhydraulic check unit 20 embodying this* rivention.- l Referring `particularly to 'Fig-v ure's Zfand 3, the ln'fdrauliccheckA unit20 islseeii to'corpri'se'a cylinder casing" 2| having-a hollow bore2 Ithereinfclesed at one end andsuccessiiely counterbored from the other'pend as indicatedl at 2I`b,-j`2tcand"2 ld.- The casing 2| atits closed end defines a -pivt bearing 21e by vvvl'iic'h the unit sjpivo'tally supported uponY the pivot Ybearing 12b ofthe" i-ihary bracket 12.- E

Aliner sleeve 23 is-inserted in the 'rs'tcounterbre2I-b of theca'sing bore 2MLy and -is rotatably adjustable therein; Such adjusttnertfrnay be effected in any convenient-manner, for example; by a'lpinion 24 which is -journal'ed in al generally radially vextending aperture 2 If provided adjacent the closed end of cylinder casing 2|. The pinion 24 is preferably manually rotatable, such a's by a ilexible"shaftd 25 which is` suitably co-rotatably secured tothe pinion 24 by a coupling 25a. Gear teeth' 23a'are' "formed on vthe end face of liner sleeve 23 andme's'h-w'ith pinion'24. Hence upon ventfpf fthe Spreker" Y rotation of the flexible shaft 25 by a suitable contr'olknob (not shown) which may be located on the machine in any convenient position for the operator, lthe angular positionv of the sleeve 23 and the' cylinder casing 'may be varied. y

A'pistonv rod 26 isl provided which is slidably jou-rnal'ed'ina sleeve bearing insertl 22a, which is in turn mounted in a central bore of a bearing support ring 22 which is "snugly mounted in the largest counterbore 2Id of casing 2| and retained therein by asnap ring v8. The inner endof piston rod *2liv is threaded as indicated at 26a, and a piston 21 is adjustably positioned on such threaded end by a pair of Vopposedpnuts 28.' The outer end offpiston rod 26 is provided with an integrally formed pivot bearing boss 2Gb by which the piston rod 26 is p'ivotally mounted to the uppermost pivot bearing 13b of the secondary bracket I3. A ccordingly, the movements of the picker stick Il relative to the primary bracket I2 will produce an-axial reciprocation of the piston'rod 26 with respect to thecylinder casing 2|.

The piston 21 is of'generally cup-shaped coni figuration and', while its bottom end face 21a is substantially perpendicular to the axis of the piston rod 26, the opposite face 21h is shaped so that at least a portion of the periphery of such facev is generally helically inclined :with respect't'o the pistonv rod axis.A For example, the inclinedface 21h" may be vformed by cutting the rim portion o f the piston 21 at an acute angle to the axis of vthe piston.

The entire interior of the piston casing 2| is filled with a suitable hydraulic uid in normal'operation. In order to provide a controlled checking action upon VVthe relative movements between the piston 21V and Athe liner sleeve 23, the liner sleeve 23' is provided with a plurality of axially spaced throttling apertures 29 and 30` respectively. Such apertures are, of course, in uid 'communication' by virtue of the fact thatt'he'y are' disposed in the counter-bored portion 2c of the cylinder casing 2l and hence substantially unimpeded fluid passage between the throttling 'apertures is provided 'exteriorly oi"tlie"liner "Sleeve'23.' It is"th'erefi"e"appaie1t ali-portions 4of its*inotve'r 6, thaty a'y Vtime uref-piston lfzi* is" positioned' in;V tjf'edit the Vthrottlng apertures '2 9 and" 30, fluid 'Will be bypassed' around thepstn byoW through the" throttli'ngiapetues '2'9 1and' -30 "and arurfltl5 theeXterr of liIiel sleeve 23.

`'Iheelectiv'e fluid passage areas ofthe throttling apertures 29 and 30 which are expos'd'in any -par'ticularlpostion of piston 21 determines the frate of, flow of fluid around the'piston and hence, determines the effective checkingactio'n exertedfuponj the axial movements ofthe piston.4v Such throttling apertures are therefore complxly shaped in an axial direction to pro'- vid the desired checking characteristics required 'in each particularaxial position of the piston v21. Thus` the throttling aperture 29,' which" isfeffeetive to check 'the inward or 'power stroke of the-picker stick 4Ii after 'the shuttle has rbe'erij thrown, has a relatively short and narrowax'ial extension 29d, so lthat the movemeritV off-the piston 21 to theleft as 'viewed in Figures" 2 and 3 is very rapidly checked after the piston once begins tov override the throt tliiig` aperture 29. In contrast, the throttling aperturevtlwhich effectsthe checking of the picker stick afterv it is contacted by theshuttle thrown from the other side ofthe loom, permits a much greater length of travel of the piston 21 and a more gradual increase of the fluid checking action. Thus' the throttling aperture 3 is provided with a tapering axial extensiona which reduces ineffective cross sectional area as in the direction of travel of theA piston 21 to ythe right as viewed in Fig'- ures 2 and 3. y

The rate of decrease of elective iiuid passage area of the throttling' aperture extension 39a is, of course, proportioned according lto Well known design procedure to provide the desired degree of `throttling at each successive axial position of thepiston 21 as the piston rod 26 moves to theright as viewed in Figures 2 and 3, so' that the piston 21, and hence the picker stick and shuttle will always be stopped at substantially the same position.

As was heretofore indicated, it is practically impossible to adjust the check unit for the picker stick of the loom to exactly provide the desired checking characteristics prior to assembling the unit iin the loomr and observation of the operation of the loom. This is vparticularly true with respect to the checking of the out- Ward stroke of the picker stick, Vwherein much Ygreater energy 'forces must be absorbedand yet the pickerstick must be accurately brought to rest in a predetermined relationship with respect to 'the shuttle box.

The described construction permits a very accurate vadju'stine'nt of the checking effects with respect tothe axial position `of thel piston 21 during the outward movement of the vpiston rod 26, which corresponds to theoutwardl movement of the pickerstick. By rotating the sleeve 23 by the described manual adjusting mechanism, the effective angular position of the throttling aperture 30 with respect to the helically extending portion 21h of the face of the piston 21 is shifted, and, as a result, a variation is effected in the amount of checking action'produced in any particular axial position of the piston 21, as it moves to the right as viewed in Figures 2 and 3. It is therefore apparent that the checking action kmay be accuratelyadjusted aftergthe kcheck unit is .asjsmliled @91115100111 arid lwhile Vth@ 1109111@ operated, angherie@variations ni' operating characteristics of the loom may be readily compensated for by adjustment of the rotational position of the sleeve 23 with respect to the piston 21.

To prevent iluid leakage from the cylinder casing 2l a sealing ring 3l is mounted in an annular groove provided in the periphery of the bearing support 22 and such link sealingly engages the cylindrical wall of the outermost counterbore 2 Id. To prevent fluid leakage along the shaft of the piston rod 26, a sealing unit 33 is mounted in surrounding relationship to such rod and disposed in a counterbore 22h formed in the outer end of the bearing support block 22. Such sealing unit may obviously comprise any one of several well known arrangements and will not therefore be described or illustrated in detail.

In the normal operation of those portions of the hydraulic check unit heretofore described, the fluid displaced by the axial movement of the piston will, of course, ilow from one end to the other of the chamber defined by the liner sleeve 23 through the flow paths provided by the throttlingapertures 29 and 36. When the hydraulic check unit is employed in applications where a small relatively slow movement of the piston rod 26 occurs, such bypass fluid flow will readily take place. However, when applied to checking the movements of a picker stick of the loom, or similar applications, the acceleration of the piston rod 26 is so rapid that an excess of fluid tends to be discharged through the throttling apertures 29 or 30 as the case may be, so that a substantial increase in iluid pressure in that portion of the check unit surrounding the liner sleeve 23 would be produced. This condition is particularly prevalent during the inward movement of the piston 21 which corresponds to the shuttle throwing stroke of the picker stick.

In addition, whether the check unit is employed in applications where rapid or slow movement of piston rod 26 occurs, it will be apparent that the volume of the cylinder chamber dened by liner sleeve 23 will be decreased each time piston rod 26 enters the chamber, therefore the hydraulic fluid will either be displaced or will undergo an increase in pressure.

Inasmuch as normal operating temperatures are in the vicinity of 150, it will be further apparent that the hydraulic fluid will tend to expand following a period of sustained operation therefore, the hydraulic fluid will either be displaced or will undergo an increase in pressure.

If the pressure of the hydraulic medium were permitted to increase, lluid resistance would interfere with the travel of the piston 21 through the intermediate portions of the stroke. Therefore, this invention provides a second sleeve 34 which is concentrically mounted with respect to the liner sleeve 23 in the second counterbore 2|c f the cylinder casing 2l The cylinder casing 2| is provided with an integral hollow protuberance 21k which denes a cylindrical reservoir chamber 21m. The protuberance 2l7c is so disposed with respect to the axis of the piston rod 26 that the axis of cylindrical reservoir chamber 2 lm is substantially vertical when the check unit is assembled in the picker stick linkage, as shown in Figure 1. Reservoir chamber 2Im is in fluid communication with substantially the entire external periphery of secondary sleeve 34 by the provision of an annular recess 2111, in the intermediate portions of the second counterbore 2lc of the cylinder casing 2 I.

Protuberance 2|k is provided with an integral top wall 21p which in turn defines a centrally disposed filling opening 2|q. lA closure plug 36 is threadably insertable in the end of illling opening 2Iq and, when the interior of the cylinder casing 2| is filled with suiilcient fluid to completely fill the spaces between the sleeves 23 and 34 and to partially fill the reservoir chamber 2 Im, a trapped air space is then defined between the level of iluid in the reservoir chamber 2Im and the closed top wall 2Ip. Such trapped air space is employed to permit ready increase in the volume of fluid contained in the reservoir chamber 23 whenever the hydraulic fluid is displaced from within the liner sleeve 23.

Fluid communication between the interior of secondary sleeve 34 and the reservoir chamber 2Im is provided by an aperture 34a in the secondary sleeve 34 which is preferably located at a remote position with respect to the reservoir chamber 2Im, such as in the bottom side of the secondary sleeve 34. Such location of the aperture 34a provides a relatively long llow path between the interior of liner sleeve 23 and the reservoir chamber 2 Im so as to substantially absorb all of the surging effects of the excess fluid pumped out of the liner sleeve 23. This damping of the surging tendencies of the iluid prevents the formations of air bubbles or frothing of the fluid in the reservoir chamber 2Im and hence prevents air from being drawn into the liner sleeve 23 where it would substantially interfere with the checking action exerted upon the piston 21.

To bleed the interior of the liner sleeve 23 and the space between liner sleeve 23 and secondary sleeve 34 of any air that may have been drawn in during operation, a restricted area passage 34d is Adeilned at one end of the sleeve 34 which communicates with a recess 2Ir milled into the outer counterbore 2id of the cylinder casing. Passage 34d also permits bleeding of air during the initial lling of the cylinder unit 2U with fluid. A fluid passage 2 Is communicates between recess 2lr and reservoir chamber 2l m. The recess 2I1' also communicates with an annular groove 2 lt provided in the outer counterbore 2 Id of the cylinder casing 2lt which, in turn, is in communication through general radial holes 22o with the sea] mounting chamber dened by counterbore 22h formed in the bearing support 22. Hence any fluid that leaks along the piston rod 26 through the bearing insert 22a will be returned to the cylinder portion of the check unit. It should be noted that radial holes 22e also serve to bleed to the reservoir chamber 2| m any air which may pass in along piston rod 26 through sealing unit 33.

To provide a convenient indication of the proper level of fluid to which the check unit must be filled, the cylinder casing protuberance 2Ilc is provided with a sleeve portion 2|w surrounding the filling opening 2| q and projecting into the interior of the reservoir chamber 2Im. The extent of projection of the sleeve portion 2| w is proportioned to correspond to the desired height of the trapped air space to be achieved within the reservoir chamber 2Im when the check unit is assembled in the picker linkage and lled with fluid. Sulcient fluid is added to the interior of the check unit 20 so as to bring the fluid level up to the bottom face of the sleeve 2lw and this level of iluid may be readily detected merely by observation through the fluid opening 2Iq. Hence, a very uniform trapped air space may be maintained within the check unit 20 throughout successive iluid filling operations and uniformity of checking action upon the picker stick linkage is therebyv assured.

It is therefore apparent that the. described check unit provides an unusually simple yet effective arrangement for accommodating the hydraulic uid displaced as a result of the accelera- `tion of piston 2l, the variations in the volume of the cylinder chamber or the variations in the volume of the hydraulic fluid. At the same time, surging of the displaced excess fluid is substantially eliminated so that no frothing of the trapped air is produced. The filling arrangement insures that a uniform trapped air space will be maintained within the check unit so as to conveniently indicate the proper lling level of fluid in the Vcheck unit. Obvious1y, the amount of fluid contained in the reservoir chamber Zlm is readily variable as a function of the pressure of such fluid, the excess fluid being conveniently accommodated merely by compressing the air contained in the trapped air space at the top of such chamber.

It will, of course, be understood that various details of construction may be modified through a wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

We claim as our invention:

1. An hydraulic check comprising a hollow casing defining a primary chamber adapted to be filled with fluid, a first sleeve mounted in said chamber, a piston reciprocable in said first sleeve, said first sleeve having throttling apertures therein to bypass fluid around said piston at a limited rate to exert a predetermined checking action on the movements of said piston, a second sleeve surrounding said first sleeve and spaced therefrom, means on said casing defining a reservoir chamber communicating with the exterior of said second sleeve, at least a portion of said reservoir chamber being disposed at a higher gravitational level than said primary chamber, a fluid charge filling both said sleeves and part of said reservoir chamber, the uppermost part of said reservoir chamber dening a trapped air space, and said second sleeve being apertured at a region remote from said trapped air space to accommodate flow of excess fluid from said primary chamber into said reservoir chamber, whereby surging of said excess fluid flow is substantially eliminated.

2. An hydraulic checking unit comprising a hollow casing defining a primary chamber adapted to be filled with fluid, a first sleeve mounted in said chamber, a piston reciprocable in said first sleeve, said first sleeve having throttling apertures therein to bypass fluid around said piston at a limited rate to exert a predetermined checking action on the movements of said piston, a second sleeve surrounding said first sleeve and spaced therefrom, said casing being additionally recessed to define a reservoir chamber above said second sleeve and communicating with the exterior of said second sleeve, said second sleeve having an aperture in the lower side thereof providing a relatively long flow path from said throttling apertures to said reservoir chamber, and a fluid charge filling both said sleeves and a portion of said reservoir chamber.

3. The combination defined in claim 2 wherein the top portions of said reservoir chamber define a trapped air space, the top wall of said reservoir chamber having a depending sleeve projecting into said reservoir chamber and defining a filling opening, the extent of projection of said sleeve into said reservoir chamber being proportioned to correspond to the desired height of the trapped air space, and closure means for said fillingopening.

4. An hydraulic check unit comprising a hollow casing defining a cylindrical bore, a liner sleeve mounted in said bore and adapted to be filled with fluid, a pistonl axially reciprocable with said liner sleeve, at least a portion of one face of the piston having a periphery generally helically disposed relative to the sleeve axis, said sleeve having throttling apertures in the wall thereof permitting fluid flow around said piston and providing controlled resistance to axial movement of said piston, means for relatively angularly shifting said piston and said sleeve, thereby varying the axial location of said piston at which a predetermined resistance to movevment of the piston is produced, a second sleeve surrounding said first sleeve and spaced therefrom, means on said casing defining a reservoir chamber communicating with the exterior of said second sleeve, at least a portion of said reservoir chamber being disposed at a higher gravitational level than said cylindrical bore, a fluid charge filling both said sleeves and part of said reservoir chamber, the uppermost part of said reservoir chamber defining a trapped air space, and said second sleeve being apertured at a region remote from said trapped air space to accommod-ate flow of excess fluid from said first sleeve into said reservoir chamber, whereby surging of such excess fluid flow is substantially eliminated.

5. An hydraulic check unit comprising a hollow casing defining a cylindrical bore adapted to be filled with fluid, a first sleeve rotatably mounted in said bore, a piston axially reciprocable in said first sleeve, at least a portion of one face of said piston -being generally helically disposed relative to the sleeve axis, said first sleeve having throttling apertures in the wall thereof permitting fluid flow around said piston to provide a controlled resistance to axial movement of said piston, said first sleeve having gear teeth on one end thereof, a pinion journalled in said casing and meshing with said gear teeth, manually operable means for rotating said pinion, thereby angularly shifting said throttling recess relative to said helical portion of said piston face, a second sleeve surrounding said first sleeve and spaced therefrom, said casing being additionally recessed to define a reservoir chamber above said second sleeve and communicating with the exterior of said second sleeve, said second sleeve having an aperture in the lower side thereof providing a relatively long flow path from said throttling apertures to said reservoir chamber, and a fluid charge filling both said sleeves and a portion of said reservoir chamber.

6. A hydraulic unit for checking and controlling a shuttle loom comprising, in combination, a closed casing adapted for mounting on a portion of the loom and having one end thereof successively counterbored to define a series of stepped cylindrical walls, a rotatable sleeve in one of said counterbores, a truncated cylindrical piston axially reciprocable in said sleeve and having a driven connection with a relatively movable portion of the loom, means for sealing the piston end of the casing, said sleeve defining axially spaced complexly shaped apertures, and means for selectively rotating said sleeve relative to said piston to vary the relative position of said apertures, thereby adjusting the checking characteristics of said unit, said casing further defining a hollow protuberance located generally at a normally upper portion of said unit and being in communication with the counterbore portions, whereby fluid displaced by said piston will be forced through said complexly shaped apertures and into said hollow protuberance.

7. A hydraulic unit for checking and controlling a shuttle loom comprising, in combination, a closed casing adapted for mounting on a portion of the loom and having one end thereof successively counterbored to dene a series of stepped cylindrical walls, an adjustable rotatable sleeve in one of said counterbores, a truncated cylindrical piston axially reciprocable in said sleeve and having a driven connection with a relatively movable portion of the loom, means for sealing the piston end of the casing, said sleeve defining axially spaced complexly shaped apertures, means for selectively rotating said sleeve whereupon said apertures will be adjustably positioned relative to said piston to adjust the checking characteristics of said unit, said casing further defining a hollow protuberance located generally at a normally upper portion of said unit and being in communication with the counterbore portions, whereby fiuid displaced by said piston will be forced through said complexly shaped apertures and into said hollow protuberance, and a second apertured sleeve in one of said counterbores surrounding said rotatable sleeve to lengthen the flow path presented to the displaced fluid between said apertures and said hollow protuberance.

8. A hydraulic unit for checking and controlling a shuttle loom comprising, in combination, a closed casing adapted for mounting on a portion of the loom and having one end thereof successively counterbored to dene a series of stepped cylindrical walls, a sleeve in one of said counterbores, a piston axially reciprocable in said sleeve and having a driven connection with a relatively movable portion of the loom, means for sealing the piston end of the casing, said piston defining a peripheral face having variable axial dimensions, said sleeve defining axially spaced complexly shaped apertures, means for selectively varying the positioning of the spaced apertures and the face of the piston to adjust the checking characteristics of said unit, said casing further defining a hollow protuberance located generally at a normally upper portion of said unit and being in communication with the counterbore portions, whereby fluid displaced by said piston will be forced through said complexly shaped apertures and into said hollow protuberance, and a second apertured sleeve in one of said counterbores surrounding said rotatable sleeve to lengthen the flow path presented to the displaced fluid between said apertures and said hollow protuberance, said protuberance defining a depending sleeve formed on the top wall thereof and constituting a uid filling opening for said hydraulic unit, said sleeve constructed to dene a visually observable fluid level whereby a uniform air space may be maintained above the body of ii-uid in said unit in the upper portion of said hollow protuberance.

9. A hydraulic unit for checking and controlling a shuttle loom comprising, in combination, a casing adapted for mounting on a portion of the loom and having a hollow bore formed therein, a rotatable sleeve in said bore, a truncated cylindrical piston axially reciprocable in said sleeve and having a driven connection with a relatively movable portion of the loom, means for sealing the piston end of the bore, said sleeve defining axially spaced complexly shaped apertures, and means for selectively rotating said sleeve relative to said piston to vary the relative position of said apertures, thereby adjusting the checking characteristics of said unit, said casing further defining a hollow protuberance located generally at a normally upper portion of said unit and being in communication with the hollow bore to receive fluid displaced by said piston through said complexly shaped apertures.

BERNARD E. OCONNOR. RICHARD E. HENRICH.

REFERENCES CITED The following references are of record in the iile of this patent:

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